Techniques are disclosed for securely classifying or decoding data. By way of example, a method of determining a most likely sequence for a given data set comprises a computer system associated with a first party performing the following steps. An encrypted model is obtained from a second party. The encrypted model is utilized to determine cost values associated with a particular sequence of observed outputs associated with the given data set. The cost values are sent to the second party. At least one index of a minimum cost value determined by the second party from the cost values sent thereto is obtained from the second party. A minimum cost sequence resulting from the at least one index is determined as the most likely sequence.